At check-ups, your baby’s weight, length and head size are plotted on a growth chart. Understanding what these charts show can take a lot of worry out of the numbers.
What does a percentile mean?
A percentile compares your baby with healthy babies of the same age and sex. On the 25th percentile for weight, 25 out of 100 babies weigh less and 75 weigh more. A baby on a low or high percentile can be perfectly healthy: what matters is steady growth.
Which charts are used?
The CDC and the American Academy of Pediatrics recommend the WHO Child Growth Standards for children under 2. They describe how healthy breastfed babies grow when their needs are met. From age 2, the CDC growth charts are usually used in the US.
What doctors look for
- A steady curve: most babies follow roughly the same percentile line over time, after settling in the first few weeks.
- Crossing lines: moving down or up across two or more major percentile lines may need a closer look.
- Very low or high values: measurements below the 3rd or above the 97th percentile are usually checked.
- How measurements relate: for example, weight compared with length.
Getting accurate measurements
Babies under 2 are measured lying down. Home scales and tape measures are less accurate than clinic equipment, so one unexpected home result is not a reason to panic. Bring your baby’s records to appointments so trends can be seen.
Premature babies
For babies born before 37 weeks, growth is plotted using corrected age, which allows for how early they were born.
Check your baby’s weight, length and head size with our Baby Growth Percentile Calculator.